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4210 24 pt. VLAN not at 1Gb

Occasional Visitor

4210 24 pt. VLAN not at 1Gb

I have a strange problem I need an explanation for. I currently have a 24 pt. 4210 switch running two VLANs, the default VLAN is the majority of the ports (1-18) and is the management VLAN. The other is a 5 port VLAN that only has two servers connected to it and its uplink.

My problem is this, the management VLAN and the web servers I have connected to it are running at 1 GB, no problem there, everything is set to Auto Detect Port Speeds BTW. But the 5 port VLAN will only run at 100Mbps. And if I try to force the ports to run at a 1000 it breaks the connection. The 6 port VLAN is configured on ports 19-23 and the only three that are connected are 21, 22 and 23. I'm positive the "feed" signal from the upstream switch is going at 1Gbps because I've moved these three connections from the VLAN on this 4210 to a 4924 configured exactly the same and all the connections run at 1Gbps. Am I missing something here? I've gone through the switch configs and cannot find anything that manages the speed of these ports in a VLAN.

Can anyone explain why the 2nd VLAN on a 3Com 4210 will NOT run at 1Gbps, but the exact same configuration on a 3Com 4924 will?

Thank you.


This message was edited by ajs15psu on 9-1-09 @ 10:32 AM
Occasional Advisor

Re: 4210 24 pt. VLAN not at 1Gb

My initial thoughts are that if your going to set the speed to 1000Mbps you should also hard set the Duplex and flow control at the same time. Also ensure that you have used "straight through" UTP cables and not crossovers for these conenctions.

If the units are anything like the 4400's



<>int interfaceX/Y/Z

<>speed 1000

<>duplex full

<>flow control


Frequent Advisor

Re: 4210 24 pt. VLAN not at 1Gb

The 4210 is a 10/100 switch with only 2 ports that can work at 1Gb. So your overview is a bit confusing.

Is this a question about port autonegotiation when manually set to 1GB on on side and auto on the other and why it works on 4924 but not on 4210. Then thats a slightyly different question.

The fix is easier than the explaination and that is to set both ends identically (either static or autonegotiation) and you should be fine. Keeping in mind the obvious of connecting a statically configured 10/100 port to a statically configured 1 GB port will never come up. Best practices state that Uplink ports and ports connected to Servers should always be statically configured not auto negotiation

A best practice is that if you manualy/statically set a port on one end to a specific speed/duplex/flow-control mode then do the same on the other end.

The explaination on the speifics of why, then depends on what specifically is connected to the other side of the link.

Is it a server? then whose and what Specific NIC is in it etc

Is it a switch? then whose and what specfic interface parameters are set and even which chipset is used for those ethernet ports etc.

Frequent Advisor

Re: 4210 24 pt. VLAN not at 1Gb

Also noticed none of the ports listed are the 2 Gig Combo ports. Therefore you will never get 1GB from them. Do you have a Copper Transciever inserted into a combo port ?

Occasional Visitor

Re: 4210 24 pt. VLAN not at 1Gb

Thanks for the info LuckyCharms. What you said makes sense. After doing some testing I found that yes you are correct, the only ports on the 4210 switch that will do a Gig are the last four, two copper and two fiber. All other standard ports will only do 100Mbps. Period! :)

Thanks for your insight. The other servers that I saw that were running at a Gig were Virtual web servers that were plugged into another 3Com 4924 that WILL do a GIG, but the one physical web server that was directly connected to the 4210 was only at 100Mbps, as it should have been.

Looks like I need a better swithc.